It is common practice to decorate the surface of manufactured articles to create an aesthetically pleasing look for the product. This has traditionally been accomplished through the use of liquid paints and clear coats, typically containing solvents that evaporate from the paint leaving behind the solids in the form of a uniform film that decorates the surface of the article.
Traditional vehicle assembly methods typically include a spray painting step to paint and/or coat visible vehicle parts and provide a protective and aesthetic appealing outer surface. However, the process of spray painting is time-consuming and generally involves volatile organic solvents that present special handling and/or environmental issues.
The transportation industry has sought to reduce solvents in vehicle assembly plants through the development and use of decorative films, known in the art as “paint films” and “paint protection films”. The original idea behind paint film was to utilize a conventional paint, which would simply be coated onto a liner and dried. The liner would then be releasably removed from the paint film which would then be applied to, for example, a three-dimensionally shaped vehicle body part. In order to improve the appearance of paints, a transparent clear coat (commonly known as a clear coat) is known to be applied onto the colored paint (commonly known as a base coat). Similarly, paint films may have a transparent clear layer disposed on a color layer. Paint protection films have a transparent clear layer, typically in combination with an adhesive layer.
However, achieving a high quality application (for example, free of wrinkles and/or puckers) remains a serious concern with paint films and paint protection films, especially if applied to large or severely contoured surfaces.
There are two predominant techniques used to manufacture paint films and paint protection films: (1) solution-casting; and (2) extrusion. Each of these processes typically requires the use of elevated temperature (120° C. to 250° C. or more) to either evaporate the solvent (solution casting) or to melt the polymer (extrusion). Such temperatures are prone to thermally inducing shifts in color and other appearance properties of paint films, making color and appearance matching difficult to achieve.
High gloss and high image clarity are among the most common requirements for automotive finishes. While solvent based paints and clear coats are typically capable of acceptable appearance, extruded plastic films fall well short of achieving a desirable rich ‘wet-look’.
If paint films or paint protection films are applied to three-dimensional shaped vehicle parts problems may be encountered such as, for example, stretching, wrinkling, and/or puckering of the film during application that renders the finished body parts aesthetically, and possibly functionally, unsuitable. These problems may be made even worse by molecular orientation of the film (for example, during extrusion) such that stretchability of the film varies with film orientation.